The "Clueless" actress — who was married to screenwriter Simon Monjack — was believed to have suffered a cardiac arrest at her home in Los Angeles when she passed away aged 32 on Dec. 20. However, the official document lists the cause of her death as "deferred" and the manner of death as "pending investigation."

Her father, Angelo Bertolotti, with whom she was estranged, is also not listed on the certificate — instead it claims he is "unknown." The actress's cousin, Tayebe Pajooh, is listed as the informant — the person who gives important details after a death — on the document.

The cause of death is expected to be confirmed when toxicology results are returned early next year.

Despite her untimely death, some of Murphy's final work may be made public. It has been reported that tracks from the actress' debut album may be released in 2010. A music executive said: "People are definitely interested in Brittany and her story. Depending on what she may have recorded and what kind of quality it is, she could end up having a hit song or two."

Since she died, there has been much speculation about Murphy's use of prescription drugs and weight issues. Ten different types of medication were confiscated from her bedroom after she was found collapsed in the shower.